This invention relates to a working apparatus of pliable structure, such as a cargo handling apparatus with a multiple degree of freedom, a robot, etc., which is equipped with an arm assembly having a plurality of arms connected together for pivotal movement.
To save labor and cope with diversification of workload in assembling and construction workstations, there has in recent years been an increasing demand for a working apparatus equipped with an arm assembly having a plurality of arms with a multiple degree of freedom. Meanwhile, one of the problems which manufacturers encounter nowadays in reducing production costs is how to obtain a light weight of this type of working apparatus.
Under these circumstances, assembling robots and coating robots have in recent years been introduced. These robots have relatively short arms which are about 2 to 3 meters in length, and no great influences are exerted on production costs even if a rigid structure with little deflection is adopted to increase the precision and accuracy with which the arms are positioned.
However, in working apparatus such as construction machines, an arm assembly having a plurality of arms of large length which are 20 to 30 meters in length and have a plurality of joints is required to handle articles of heavy weight. In this type of working apparatus, it is impossible to adopt a rigid structure as is the case with the assembling and coating robots referred to hereinabove, because the size of the arms would have to be increased and an increase in the size of the arms would require an increase in the size of actuators for driving the arms. This would inevitably result in a rise in production costs. After all, the use of a rigid structure in this type of working apparatus would be economically unfeasible. This has prompted one to try to adopt a pliable structure for a working apparatus in which the arms have minimized dimensions (including the width). The problem encountered in working apparatus of pliable structure is that difficulty is experienced in achieving a high degree of precision and accuracy in positioning the arms because of the possibility of inevitable deflection of the arms.